Recently, as wireless communication services have been generalized, and wireless broadband data communication has been activated, various frequency bands become available frequency bands in order to sufficiently secure insufficient frequency bands. A mainly used frequency band is a band of 800 MHz or 900 MHz (for example, 698 to 940 MHz, hereinafter, referred to as “a first frequency band”) that is a relatively low frequency band, a band of 1.8 GHz or 2.1 GHz (for example, 1.71 to 2.17 GHz, hereinafter, referred to as “a second frequency band”) that is a relatively high frequency band, and a band of 2.3 GHz (for example, 2.3 to 2.7 GHz, hereinafter, referred to as “a third frequency band”) that is a relatively high frequency band. The first, second, and third frequency bands are appropriately distributed and allocated to communication schemes according to second generation (2G, for example, CDMA), third generation (3G, for example, WCDMA), and fourth generation (4G, for example, LTE) wireless access technologies (Radio Access Technology (RAT)), respectively. Further, the MIMO technology based on multiple antennas is an essential technology in improving a data transmission speed, and has been applied to a recent wireless communication network, such as LTE and Mobile WiMAX.
FIG. 1 is a block diagram illustrating an example of wireless access node systems for each of a plurality of business operators representing a general antenna installation state, and illustrates, for example, a base station system A 10 and a base station system B 20 which are wireless communication base stations of business operators A and B. In this case, the base station system A 10 and the base station system B 20 may be general wireless communication base stations taking charge of a relatively wide area, but in the example of FIG. 1, the base station system A 10 and the base station system B 20 are installed in each floor of a building, such that the base station system A 10 and the base station system B 20 correspond to a relay station or a small base station installed in a specific shadow area 1.
Referring to FIG. 1, each of the base station system A 10 and the base station system B 20 may include, for example, communication equipment of the first to third bands. In this case, sub bands are differently allocated for each of the business operators in each of the first to third bands, so that the base station system A 10 includes transceiving units 1-A, 2-A, and 3-A, 110, 120, and 130 for processing transceiving signals of bands 1-A, 2-A, and 3-A. Similarly, the base station system B 20 includes transceiving units 1-B, 2-B, and 3-B 210, 220, and 230 for processing transceiving signals of bands 1-B, 2-B, and 3-B. For example, the band 1-A may be set to have a transmission band of 824 to 839 MHz, and a reception band of 869 to 884 MHz, and the band 1-B may be set to have a transmission band of 839 to 849 MHz, and a reception band of 884 to 894 MHz.
A transmission signal of each of the different bands processed by the transceiving units 1-A, 2-A, and 3-A 110, 120, and 130 of the base station system A 10 is coupled by a filter coupler 140 and transmitted to one or more base station antennas A 12 installed in the shadow area 1 (for example, a specific layer of a building), and the signals received by the antenna 12 are distributed for each frequency by the filter coupler 140 and provided to the transceiving units 1-A, 2-A, and 3-A 110, 120, and 130, respectively. Similarly, the base station system B 20 also includes a filter coupler 240 for distributing and coupling transmission and reception signals between the transceiving units 1-B, 2-B, and 3-B 210, 220, and 230 and one or more base station antennas B 22 installed in the shadow area 1.
The filter couplers 140 and 240 of the base station systems A and B 10 and 20 are implemented in a filter coupled structure similar to a structure of a duplexer and a multiplexer for no-loss coupling and distributing the transmission and reception signals. In this case, each of the filter couplers 140 and 240 serves as a distributor as it is without a change of a structure thereof when a signal input/output direction is simply changed, and it may be understood that a term “coupler” actually means a “coupler/distributor”. An example of a technology for a filter coupler is Korean Patent Application Publication No. 10-2008-0114104 previously filed by the applicant of the present application (title: “Filter Combiner/Divider”, inventors: PARK, Sang-Sik and YANG, Myeong-Hoon, publication date: Dec. 31, 2008).
In the meantime, the structure illustrated in FIG. 1 is the example implemented by a 1Transfer 1Receive (1T1R) scheme, not the MIMO scheme. That is, for example, only a first transception path (path1) P1 is connected with the filter coupler 140 in the transceiving units 1-A, 2-A, and 3-A 110, 120, and 130 of the base station system A 10. In the structure, when the MIMO scheme, such as a 2Transfer 2Receive (2T2R), is implemented, an additional filter coupler and additional antennas are provided for processing a transmission/reception signal for a second transceiving path P2 of the transceiving units 1-A, 2-A, and 3-A 110, 120, and 130 of the base station system A 10.
As illustrated in FIG. 1, in a general wireless communication system, a plurality of business operators generally provide services, and the business operators individually install the independent base station systems 10 and 20 and the antennas 12 and 22 to provide the services, respectively. Accordingly, there are problems in that a wave quality is degraded due to mutual interference of the base stations separately installed for each business operator and investment is repeated and excessive. Particularly, a cost for installing the plurality of antennas for each business operator is increased, and there is a large problem in securing a space for actually installing an antenna and efficiency of a management of the antenna.
Further, recently, a demand for supporting MIMO in various frequency bands has risen, and to this end, when antennas are installed for each business operator, the aforementioned problem becomes more severe.